Rename buildflag_headers for consistency

This updates ppapi.

Targets go from foo_features to foo_buildflags
And similarly the header now has buildflags in the name.

BUG=814485
TEST=covered by build
[email protected]

Change-Id: I25f990ebd1e7f8530ddd0cee24dba31c88a45fae
Reviewed-on: https://chromium-review.googlesource.com/980921
Reviewed-by: Scott Violet <[email protected]>
Reviewed-by: Xiaohan Wang <[email protected]>
Reviewed-by: Daniel Cheng <[email protected]>
Commit-Queue: Scott Violet <[email protected]>
Cr-Commit-Position: refs/heads/master@{#546312}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index 3bc58b8..be1e301 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -111,7 +111,7 @@
 #include "content/public/browser/render_process_host.h"
 #include "extensions/buildflags/buildflags.h"
 #include "net/http/http_server_properties_manager.h"
-#include "ppapi/features/features.h"
+#include "ppapi/buildflags/buildflags.h"
 #include "printing/features/features.h"
 #include "rlz/features/features.h"